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What’s new and what questions remain since our previous meeting?

What’s new and what questions remain since our previous meeting?. Workshop on Physics at the End of the Galactic Cosmic-ray Spectrum April 26-30, 2005. Outline. Below the knee Knee region Sources & acceleration mechanisms End of galactic cosmic-ray population?

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What’s new and what questions remain since our previous meeting?

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  1. What’s new and what questions remain since our previous meeting? Workshop on Physics at the End of the Galactic Cosmic-ray Spectrum April 26-30, 2005 Tom Gaisser

  2. Outline • Below the knee • Knee region • Sources & acceleration mechanisms • End of galactic cosmic-ray population? • Where is transition to extra-galactic? • What is the nature of the ankle? • Extra-galactic cosmic rays and GZK • Lessons from the heliosphere (2nd edition) Tom Gaisser

  3. Final Results of RUNJOB and Related TopicsMakoto Hareyama, Toru Shibata and the Runjob collaboration (Aspen, 2005) Observed spectrum ~ E(-2.7) to 100 TeV JACEE and results of other balloon experiments ~100 TeV reported by M. Cherry, Aspen 2005 Tom Gaisser

  4. All particle spectrum Note difference between JACEE and RUNJOB for ~100 TeV helium Tom Gaisser

  5. ATIC, John Wefel, Tokyo ’07 (also discussed in Cherry’s talk, Aspen 2005) Helium more like JACEE ? Hard all-nucleon spectrum? Tom Gaisser

  6. = sum of TRACER: O + Ne + Mg + Si + S + Ar + Ca + Fe TRACER(heavy nuclei only) Tom Gaisser

  7. HESS Direct Cherenkov measurement of Fe spectrum F. Aharonian et al. PR D75 042004 (2007) Method proposed by Kieda, Swordy & Wakely, 2001: Use ACT on ground. Previously attempted from balloons, Sood, 1983; Clem, Evenson, Seckel, 2002 Tom Gaisser

  8. Inferred spectrum with QGSjet Inferred spectrum with SIBYLL H.E.S.S. Direct Cherenkov Fe spectrum measurement Consistent with RUNJOB Tom Gaisser

  9. Standard model of cosmic-rays to ~100 TeV • Diffusive shock acceleration in galactic SNR • 15 % of energy goes into accelerated p & nuclei • dN / dE ~ E(-2.1) (source spectrum) • secondary / primary nuclei  tesc ~ E(-0.6) to make dN / dE (observed) ~ E(-2.7) • Problems: (e.g. Ptuskin et al., Jokipii) • strong energy dependence of tesc violates observed isotropy when extrapolated to PeV • observed turbulence prefers tesc ~ E(-0.3) • high efficiency  non-linear acceleration  event flatter source spectrum Tom Gaisser

  10. Rigidity-dependence Peters cycle: systematic increase of < A > approaching Emax • Acceleration, propagation • depend on B: rgyro = R/B • Rigidity, R = E/Ze • Ec(Z) ~ Z Rc • rSNR ~ parsec •  Emax ~ Z * 1015 eV • 1 < Z < 30 (p to Fe) • Slope change should occur within factor of 30 in energy • With characteristic pattern of increasing A • Problem: continuation of smooth spectrum to EeV B. Peters, Nuovo Cimento 22 (1961) 800 Tom Gaisser

  11. Composition in the knee region SPASE-AMANDAB10, superimposed on data summary of Swordy et al., Astropart. Phys. 18 (2002) 129. EASTOP, M. Aglietta et al., Astropart. Phys. 20 (2004) 641 Tom Gaisser

  12. KASCADE: Energy spectra for individual elemental groups c2 distribution c2 distribution ! ! SIBYLL Andreas Haungs Aspen, 2005 QGSJET H. Ulrich et al., Int. J. Mod. Phys. A (in press)

  13. What interaction model to use? • In KASCADE data, both QGSjet01 and SIBYLL have problem areas • The greater energy reach of KASCADE-Grande may help unscramble this • Xmax deeper in atmosphere, fluctuations less severe • Gives a longer range of energy over which to test the models • Hope to hear KASCADE-Grande results here at Aspen 2007 Tom Gaisser

  14. Maximum energy for acceleration by SNR shocks • Magnetic field amplification (Bell et al.) much discussed at Aspen 2005 • See paper of Hillas, for example. • Emax > PeV for protons no problem • Non-linear diffusive shock acceleration • H. Völk et al. (also Blasi et al.) • Most of energy content may be near Emax • Do we need a galactic “component B” Tom Gaisser

  15. Cosmic-ray energy spectrum (Aspen, 2005) ? J Hörandel Tom Gaisser according to Astropart. Phys. 19 (2003) 193

  16. HILLAS (Aspen, 2005)

  17. Atoyan (Aspen, 2005) Model: GRB origin of CRs at and above the knee • Cosmic Rays below ≈ 1014 eV from SNe that collapse to neutron stars • Cosmic Rays above ≈ 1014 eV from SNe that collapse to black holes • CRs between knee and ankle/second knee from GRBs in Galaxy • CRs at higher energy from extragalactic/ cosmological origin (Wick et al. 2004) Tom Gaisser

  18. BEREZINSKY TRANSITION The galactic component at E ≥ 1×1017 eV is assumed to be iron nuclei. The spectrum is found as difference of the total (observed) spectrum and extragalactic proton spectrum (model). Ec is considered as a free parameter in a range (0.3 - 2)×1018 eV Tom Gaisser

  19. GZK feature recovery (depends on source density) Distant sources Contribution depends on evolution and propagation in Bextra-galactic Nearby sources clustering, anisotropy? (de) constructing the extra-galatic spectrum dip (due to pair production) End of Galactic population (not shown) Doug Bergman et al. (HiRes), Proc 29th ICRC, 7 (2005) 315 Tom Gaisser

  20. BERGMAN Best USM Fit to HiRes • Fit USM varying m and g • g = 2.38 • m = 2.55 • Galactic spectrum falls steeply above 100 PeV Extragalactic Galactic Tom Gaisser

  21. Bahcall & Waxman (GRB) Physics Letters B556 (2003) 1 • Galactic extragalactic transition ~ 1019 eV • Assume E-2 spectrum at source, normalize @ 1019.5 • 1045 erg/Mpc3/yr • ~ 1053 erg/GRB • Evolution ~ star-formation • GZK losses included Bahcall & Waxman hep-ph/0206217 Tom Gaisser

  22. Transition < 1018 eV Transition at 1019 eV N Busca, WG-4, Aug 29 Allard et al. astro-ph/0605327 Tom Gaisser

  23. HiRes new composition result: transition occurs before ankle Original Fly’s Eye (1993): transition coincides with ankle 0.3 EeV 3 EeV G. Archbold, P. Sokolsky, et al., Proc. 28th ICRC, Tsukuba, 2003 Where is transition to extragalactic CR? Stereo Tom Gaisser

  24. KASCADE-Grande IceCube Muon / electron ratio reflects nuclear composition of primaries Calculations of Ralph Engel, presented at Aspen, April, 2005 Tom Gaisser

  25. Simulations: Em at 2 km in IceCube vs Energy deposited in tanks Projection on mass axis E A 0.64, 0.8, 1.0, 5.0, 6.25, 10, 12.5 PeV Projection on energy axis Tom Gaisser

  26. AGASA, HiRes, Auger Auger spectrum, from Paul Sommers’ talk at Pune Tom Gaisser

  27. HiRes GZK cutoff (astro-ph/0703099) E3 x differential spectrum Integral spectrum / E-1.81 Tom Gaisser

  28. Lessons from the heliosphere • ACE energetic particle fluences: • Smooth spectrum • composed of several distinct components: • Most shock accelerated • Many events with different shapes contribute at low energy (< 1 MeV) • Few events produce ~10 MeV • Knee ~ Emax of a few events • Ankle at transition from heliospheric to galactic cosmic rays R.A. Mewaldtet al., A.I.P. Conf. Proc. 598 (2001) 165 Tom Gaisser

  29. Solar flare shock acceleration Coronal mass ejection 09 Mar 2000 Tom Gaisser

  30. SOHO/ LASCO CME of 06-Nov 1997 Tom Gaisser

  31. LASCO event of 23 Nov 97 http://lasco-www.nrl.navy.mil/best_of_lasco_apr98/index.htm Tom Gaisser

  32. Heliospheric cosmic rays • ACE--Integrated fluences: • Many events contribute to low-energy heliospheric cosmic rays; • fewer as energy increases. • Highest energy (75 MeV/nuc) is dominated by low-energy galactic cosmic rays, and this component is again smooth • Beginning of a pattern? R.A. Mewaldtet al., A.I.P. Conf. Proc. 598 (2001) 165 Tom Gaisser

  33. Examples of power-law distributions(M.E.J. Newman, cond-mat/0412004) Tom Gaisser

  34. More examples from M.E.J. Newman, cond-mat/0412004

  35. Casualties per attack in Iraq(Neil F. Johnson, et al., from APS News, 8 Nov 2006) Differential a ~ 2.5 Tom Gaisser

  36. B E-G A Tom Gaisser

  37. Three classes of sources Tom Gaisser

  38. Outstanding issues • Direct measurements for calibration • Isotropy / propagation problem • Non-linear acceleration  hard spectrum • How many sources? • What interaction model to use? • Is there a component “B”? • Where is transition to extra-galactic Tom Gaisser

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